1. Field of the Invention
The present invention relates to a synthetic resin-made fastening-limiting device for a joint fastening member which fastens a pipe to be connected to a pipe receiving port on the side of a joint via a fastening member screwed to the pipe receiving port, thereby ensuring the sealing property and preventing the pipe from slipping off.
2. Description of the Prior Art
Piping for transporting a fluid which is used in a semiconductor production process is often required to have chemical resistance and corrosion resistance. In consideration of the particularity of the use environment, a synthetic resin-made pipe which has certain properties is used as piping of this kind. Similarly, as the material of joints which are interposed in many connecting and branching portions of such a pipe (including joints which are integrally attached to valves and the like connected to the pipe), synthetic resin is used having certain properties. In the connection of such a joint and the pipe, a connection structure is often employed in which, by the fastening force exerted by a fastening member such as a pressing ring screwed to a pipe receiving port on the side of the joint, the pipe inserted into the pipe receiving port is prevented from accidentally slipping off and the sealing property of the connection portion is ensured. In the connection structure, the function of preventing accidental slipping-off of the pipe due to the fastening of the fastening member, and the performance of ensuring the sealing property of the pipe connection portion are exerted only after the contact pressure which is generated by the fastening of the fastening member reaches a reference contact pressure.
When such a connection structure is employed, conventionally, means for defining the degree of the fastening force of the fastening member to an appropriate level in order to prevent the pipe from slipping off and ensure the sealing property is realized by a method such as that in which the fastening member is screwed by using a torque wrench, or that in which, when the fastening member is to be screwed to the pipe receiving port, the fastening member is caused to make a predetermined number of rotations.
However, such methods including the method in which a torque wrench is used, and that in which the fastening member makes a predetermined number of rotations have a problem in that these methods are cumbersome and require skill.
When existence/nonexistence of a forget of fastening of forgetting to fasten the fastening member, or the adequateness of the fastening state of the fastening member is to be determined, cumbersome checking must be conducted using tools and jigs. Therefore, it is difficult to completely eliminate an accident due to forgetting to fasten or a failure of fastening.